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알칼리형 연료전지에서 산소환원에 미치는 촉매 특성 연구 Ⅱ . XRD , TG , TPR 를 이용한 La0.6Sr0.4Co1 - xFexO3 의 특성 분석
문형대,이호인 ( Hyeung Dae Moon,Ho In Lee ) 한국공업화학회 1996 공업화학 Vol.7 No.3
페롭스카이트 La_0.6 Sr_0.4 Co_(1-x) Fe_xO₃(x=0.00, 0.01, 0.10, 0.20, 0.35, 및 0.50)를 산소전극물질로 사용하여 알칼리형 연료전지에서의 산소환원반응을 연구하였다. Fe치환에 따른 촉매특성의 변화를 X-선회절분석법(XRD), 열중량분석법(TG) 및 승온환원법(TPR)을 통하여 조사하였다. XRD 구조분석을 통하여 페롭스카이트 단위격자의 격자상수값을 측정할 수 있었다. TG 실험결과 Fe는 페롭스카이트 구조내에서 크게 안정화되어 900℃까지 거의 환원되지 않았고, Fe치환량 증가에 따라 Co-O간의 결합에너지가 증가하여 고온에서 제거되는 산소종의 양이 증가하였다. TPR 실험결과, α-(저온피크)와 β-(고온피크)산소종이 존재하였다. β-산소종은 Co와 강하게 결합되어 있는 산소종으로서 Fe치환량 증가에 따라 결합세기가 증가하였다. α-산소종은 가역적으로 격자내외를 출입하는 산소환원반응의 활성종이었으며, Fe치환량 증가에 따른 격자상수의 증가는 금속과 α-산소종간의 결합에너지로 볼 수 있는 α산소종의 환원피크를 저온으로 이동시킴으로써 산소환원반응의 활성을 증가시켰다. 반면에, Fe치환량 증가에 따른 α-산소종의 감소는 산소환원반응의 활성을 감소시켰으며, Fe치환에 따른 표면적의 증가는 반응활성에 크게 영향을 미치지 못하였다. Oxygen reduction in an alkaline fuel cell was studied by using perovskite of La_0.6 Sr_0.4 Co_(1-x) Fe_xO₃(x=0.00, 0.01, 0.10, 0.20, 0.35, and 0.50) as an oxygen electrode catalyst. The changes in the catalytic properties as a function of Fe content were investigated by XRD, TG, and TPR. XRD patterns gave different lattice parameters of the catalysts. TG study revealed that Fe was so stabilized in the perovskite structure as to be hardly reduced even up to 900 ℃, and the amount of oxygen which was eliminated at high temperature increased with the fraction of Fe because Fe induced the increase of Co-O binding energy. From TPR study, α-(low temperature peak) and β-(high temperature peak)states were observed. The bond strength of the β-species which was associated strongly with Co of the perovskite increased proportionally with the fraction of Fe. The α-species, reversible oxygen, was the active species in the oxygen reduction. The α-peak temperature which reflected the binding energy between Co and α-state oxygen moved to lower temperature with the increase of lattice parameter of the catalytst due to the increase of Fe content. The decrease in the binding energy increased the activity in the oxygen reduction, but the decrease of α-species with the increase of Fe content decreased the activity. The increase in the surface area with Fe content had little effect on the activity.
용융탄산염 연료전지용 내부개질 촉매의 활성에 미치는 귀금속 첨가 효과
이호인,문형대,정창렬 한국공업화학회 1997 응용화학 Vol.1 No.2
Doping effects of noble metals on Ni/MgO(Im-LPO) catalysts for internal steam reforming in molten carbonate fuel cell(MCFC) were studied. Pt-Ni/MgO catalysts exhibited higher activity for steam reforming of mathane and higher resistance to electrolyte vapor deposition than Pd-Ni/MgO catalysts. For Pt-Ni/MgO catalysts, the peak shifts to lower temperatures in TPR curves with the increase of Pt doping could be explained as followed: Hydrogen spilled over from platinum to nickel, and platinum modified the lattice structure of nickel, which enabled nickel to reduce more easily. For Pd-Ni/MgO catalysts, on the other hand, the amount of palladium doped was so small that palladium didn't seem to affect the reduction of nickel.
용융탄산염 연료전지용 내부개질 촉매에 미치는 Gd2O3 첨가의 효과와 수증기 / 탄소 비의 영향
이호인,신영준,문형대,정창렬,최재식 한국공업화학회 1998 응용화학 Vol.2 No.2
Doping effects of Ln₂O₃(Ln : lanthanide) on the activity of Ni/Mg(Im-LPO) catalysts for internal steam reforming in molten carbonate fuel cell (MCFC) were studied. The precursors of the catalysts were prepared by impregnation - liquid phase oxidation method. After heat treatment under hydrogen atmosphere, Gd existed as Gd₂O₃. The Gd₂O₃-Ni/MgO catalysts exhibited higher activity for steam reforming of mathane than the order Ln₂O₃-Ni/MgO catalysts, and the 10G25N-M catalyst exhibited the highest activity among the other _xG25N-M catalysts and also a high H₂/CH₄ value. As the increase of amount of Gd, the H₂/CH₄ value also increased. Doping of Gd₂O₃ reduced the coke formation on Ni/MgO catalysts, and the optimal S/C value for the _xG25N-M catalysts in the reaction was 3.